If you enter a coffee shop on any given morning in Brisbane, you're likely to hear people pleading for their favourite tall-skinny-half-strength-mocha-latte, or something of the like, to get them through the morning.

While some research suggests small amounts may be beneficial to our health, a new study says drinking four cups of coffee a day could be toxic.

A joint research initiative by the University of Queensland and the University of South Carolina in the United States says more than four cups a day could be bad for the health of under 55s.

UQ's Dr Carl Lavie from the Department of Cardiovascular Diseases at the Ochsner Medical Center in New Orleans says the study suggested heavy coffee consumption could be toxic to younger people.

"We followed 45,000 people, where the data was mostly collected in the early 1970s, and followed the people for an average of 17 years for both cardiovascular mortality and total mortality," he says.

"The men [under 55 years old] who reported 28 cups of coffee or more [per week] had a 56 per cent increased mortality and the younger women who reported this amount of coffee consumption actually had an over two-fold, over 100 per cent, increase in mortality risk.

"We didn't find any significant increase in mortality risk associated with any dose of coffee in anyone over the age of 55."

Dr Lavie says research results seem to suggest that small amounts of coffee do not appear to be detrimental to your cardiovascular health, at any age.

Tegan Watson, a barista at a South Bank coffee shop in one of Brisbane's main restaurant precincts, says on average not many of her regular customers would drink more than four cups of coffee a day.

"We usually find on Mondays and Fridays people actually do have a higher intake of coffee, they might ask for an extra shot or syrup."

Tegan says she is well aware of the coffee habits of her customers.

"In the morning most people like to get a coffee to wake them up and in the afternoon to get them through the day."

Mr Lavie says it's important to remember the report simply highlighted that high amounts of coffee consumption can be associated with the higher death rate in under 55s, but it's not necessarily the cause.

"We just showed that the younger people who reported drinking very high amounts of coffee had higher death rates," he says.

"We don't want to go overboard and scare people about the risk of coffee but I think there is reason to consider moderation."

Tegan says now she is aware of the research, she would consider tactfully making her under 55 customers aware of the potential risks.

"If I drank coffee, with the research, I wouldn't [drink more than four cups a day] if it's that harmful, it's not really worth it," she says.

For the record, Tegan prefers to drink peppermint tea but she makes a perfect cappuccino.